diff --git a/src/net/tools/naive/naive_proxy.cc b/src/net/tools/naive/naive_proxy.cc
index a38f791249..b4d5feee68 100644
--- a/src/net/tools/naive/naive_proxy.cc
+++ b/src/net/tools/naive/naive_proxy.cc
@@ -5,6 +5,7 @@
 
 #include "net/tools/naive/naive_proxy.h"
 
+#include <algorithm>
 #include <utility>
 
 #include "base/bind.h"
@@ -34,7 +35,7 @@ NaiveProxy::NaiveProxy(std::unique_ptr<ServerSocket> listen_socket,
                        const NetworkTrafficAnnotationTag& traffic_annotation)
     : listen_socket_(std::move(listen_socket)),
       protocol_(protocol),
-      concurrency_(concurrency),
+      concurrency_(std::min(4, std::max(1, concurrency))),
       resolver_(resolver),
       session_(session),
       net_log_(
diff --git a/src/net/tools/naive/naive_proxy_bin.cc b/src/net/tools/naive/naive_proxy_bin.cc
index 00acd7756b..4ba08712dd 100644
--- a/src/net/tools/naive/naive_proxy_bin.cc
+++ b/src/net/tools/naive/naive_proxy_bin.cc
@@ -289,7 +289,7 @@ bool ParseCommandLine(const CommandLine& cmdline, Params* params) {
 
   if (!cmdline.concurrency.empty()) {
     if (!base::StringToInt(cmdline.concurrency, &params->concurrency) ||
-        params->concurrency < 1) {
+        params->concurrency < 1 || params->concurrency > 4) {
       std::cerr << "Invalid concurrency" << std::endl;
       return false;
     }